The present invention relates generally to optical fiber connectors of the type used to connect multiple optical fibers or ribbon fibers.
Optical fiber connectors are known in which each half of the connector comprises a ferrule in which a plurality of optical fibers are terminated. The ferrule is mounted in a housing with a small amount of free play, and is biased by a spring into a forward position in the housing. The outer end face of the ferrule is exposed for face to face contact with the ferrule end face in the mating opposite half of the connector. Each fiber is terminated at a respective contact face at the outer end of the respective ferrule, and the optical contact faces engage one another to provide optical communication between the connector halves when mated together. The arrangement is such that the ferrules will be moved back slightly when the connection is made, compressing the biasing springs and ensuring a good optical contact between the fiber end faces. This type of optical fiber connector can connect a ribbon fiber containing up to 48 fibers.
One problem with known connectors for connecting a plurality of optical fibers is potential misalignment, side loading and torque in the connection. One reason for this is that the spring end acting on the inner end face of the ferrule does not present a flat surface, and thus may tend to apply some side loading or torque to the ferrule.
It is an object of the present invention to provide a new and improved optical fiber connector assembly.
According to the present invention, an optical fiber connector assembly is provided, which comprises a first unit having a first housing with a through bore and a first ferrule movably mounted in the through bore for movement between an advanced and retracted position, the ferrule having a forward end face, a second unit for releasable mating engagement with the first unit, the second unit having a housing with a through bore and a second ferrule mounted in the through bore having a forward end face for face to face engagement with the forward end face of the first ferrule when the units are mated together, each ferrule having a plurality of optical contacts at its end face for optical contact with the contacts in the end face of the opposing ferrule when the units are connected together, the arrangement being such that the ferrules are pushed back into a retracted position when the units are mated together, the first ferrule having a rear end face, and a biasing device mounted in the through bore behind the first ferrule and bearing against the rear end face of the ferrule to bias it towards its forward position, the biasing device comprising a spring having a rear fixed end and a forward end, a bushing having a front end and a rear end, the forward end of the spring bearing against the rear end of the bushing, the front end of the bushing having a part spherical seat, and a ball member rotatably seated in the seat at the forward end of the bushing, the ball member having a flat face bearing against the rear face of the ferrule.
This arrangement provides a biasing force in a direction perpendicular to the end face of the ferrule, reducing the risk of misalignment between the optical contacts, and avoiding torque or twisting forces which may result in improper alignment. The flat face of the ball member will be in full face to face contact with the flat rear end face of the ferrule at all times. The ball and socket type engagement between the bushing and ball member will compensate for any non-perpendicular force applied by the end of the spring on the bushing. The assembly will act in the manner of a universal joint to allow better alignment between the optical contacts.
In an exemplary embodiment of the invention, the connector assembly is an optical fiber assembly, and a plurality of optical fibers extend through the respective ferrule and have end faces terminated at the respective ferrule end face. Preferably, the second ferrule is also slidably mounted in the second housing for movement between advanced and retracted positions, and spring biased towards the advanced or forward position by a biasing device identical to that in the first housing. The amount of movement provided on each side of the connector is very small, preferably of the order of fifty thousandths of an inch, and the movement together with the spring loading of the ferrules ensures good face to face contact between the optical contacts.
To improve optical performance, the mating end faces of the two ferrules may in some cases each be angled slightly. One of the end faces has a pair of alignment pins projecting outwardly, while the other end face has alignment holes for receiving the pins as the units are mated together, to ensure proper alignment of the optical contacts. It is these pins that cause the fined mechanical alignment of the ferrules. But even with the pins, which have some small clearance with the bores, mis-alignment of the ferrules can occur if there is axial or rotational mis-alignment, or axial tilting between the ferrules. The universal joint like connection at the ball member allows compensation for any such mis-alignments with the ball member swiveling to allow proper alignment of the pins in the alignment holes. This ensures that the optical contacts are properly aligned.
In an exemplary embodiment of the invention, each bushing and ball member has a through bore and each ferrule has a rearwardly projecting tail portion which engages in the through bore for locating purposes. A plurality of optical fibers extend into each housing through bore, through the bushing and ball member through bores, and through the ferrule, with each fiber being terminated in a respective optical contact at the mating end face of the respective ferrule.
The optical fiber connector assembly of this invention reduces the risk of misalignment or torque on the fibers which could result in previous ribbon fiber connectors where the non-flat end face of the biasing spring bore directly against a flat end face of the ferrule. In this invention, a flat end face of an otherwise spherical ball member bears against the flat rear end face of the respective ferrule, and the ball member engages in a radiused seat at one end of bushing which is biased by the spring. This provides a universal joint type of connection, allowing much better alignment of the ferrule end faces and helping to ensure that the spring applies an axial biasing force to the ferrule.